This invention relates generally to slide valves and more particularly concerns cold wall slide valves.
Some typical slide valves and improvements to slide valves are shown in my U.S. Pat. Nos. 4,378,817, 4,615,506 and 4,671,313.
In a typical hot wall application for a slide valve, the difference in temperature between the gated fluid and the external valve body is not so significant as to produce any appreciable relative contraction or expansion between valve components as to require complex and expensive engineering to compensate for the variations. Consequently, a relatively simple and inexpensive carbon steel valve is adequate to most hot wall valve applications.
However, in cold wall valve applications, the difference in temperature between the gated fluid and the exterior valve wall can be substantial. For example, a cold wall valve may typically be used at approximately 1600.degree. F. fluid temperature and approximately 600.degree. F. exterior valve wall temperature.
One present solution deals with this difficulty by using stainless rather than carbon steel in the valve components and essentially eliminating the effects of temperature change. This choice of materials, of course, is a compromise to necessity that greatly increases the cost of the valve.
Another solution is to make a slide valve of carbon steel components but to line the interior surface of the valve wall with an erosion resistant refractory or insulation to provide a heat sink between the gated fluid and the valve wall. Usually, the valve employs a refractory lined orifice which is sandwiched between a bed plate and fixed supports above and below the orifice. The bed plate is fixed to the refractory lining the valve wall. However, over a wide temperature differential between the gated fluid and the valve wall, the refractory may expand or contract by as much as 3/8 of an inch or more. Consequently, the bed plate becomes a floating plate and the valve mechanism for gating fluid through the orifice must also be designed to float in order to achieve satisfactory valve operation.
A further problem sometimes experienced with slide valves is that their orifice supports are mounted on gusset plates welded to the interior surface of the valve wall and heat transfer frequently causes the welds between the gussets and the valve wall to crack or break.
Accordingly, it is a primary object of this invention to provide a cold wall slide valve having a fixed bed plate. It is a further primary object of this invention to provide a cold wall slide valve which minimizes failure of the gusset plate welds. And it is among the objects of this invention to provide a cold wall slide valve which can be made of relatively inexpensive materials, with relatively simple components and effective over a wide temperature differential.